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Re: hash index improving v3

From: "Alex Hunsaker" <badalex(at)gmail(dot)com>
To: "Xiao Meng" <mx(dot)cogito(at)gmail(dot)com>
Cc: "Zdenek Kotala" <Zdenek(dot)Kotala(at)sun(dot)com>, pgsql-patches(at)postgresql(dot)org, "Jonah H(dot) Harris" <jonah(dot)harris(at)gmail(dot)com>, "Tom Lane" <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Subject: Re: hash index improving v3
Date: 2008-09-05 20:21:36
Message-ID: 34d269d40809051321w2ed16037od0373a4a29c311f1@mail.gmail.com (view raw or flat)
Thread:
Lists: pgsql-hackerspgsql-patches
Ok now that I made it so it actually *test* collisions, with the patch
it always returns all rows that matched the hashed "key".  For example
(non lobotomized inthash8, I just brute forced some collisions for 0
so that anyone can try this)

create table test_hash (num int8);
insert into test_hash (num) values (0), (1805671691), (3294821164),
(4294967297);
create index test_hash_num_idx on test_hash using hash (num);
select * from test_hash where num = 0;
    num
------------
          0
 1805671691
 3294821164
 4294967297

set enable_bitmapscan to off;

select * from test_hash where num = 0;
 num
-----
   0

CVS HEAD, 8_3_STABLE obviously work if I force the index scan

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